title: Exposure to grain dust and microbial components in the Norwegian grain and compound feed industry.
abstract: OBJECTIVE
  The aim of this study was to extensively characterize grain workers' personal exposure during work in Norwegian grain elevators and compound feed mills, to identify differences in exposures between the workplaces and seasons, and to study the correlations between different microbial components.
  
  
  METHODS
  Samples of airborne dust (n = 166) were collected by full-shift personal sampling during work in 20 grain elevators and compound feed mills during one autumn season and two winter seasons. The personal exposure to grain dust, endotoxins, β-1→3-glucans, bacteria, and fungal spores was quantified. Correlations between dust and microbial components and differences between workplaces and seasons were investigated. Determinants of endotoxin and β-1→3-glucan exposure were evaluated by linear mixed-effect regression modeling.
  
  
  RESULTS
  The workers were exposed to an overall geometric mean of 1.0mg m(-3) inhalable grain dust [geometric standard deviation (GSD) = 3.7], 628 endotoxin units m(-3) (GSD = 5.9), 7.4 µg m(-3) of β-1→3-glucan (GSD = 5.6), 21 × 10(4) bacteria m(-3) (GSD = 7.9) and 3.6 × 10(4) fungal spores m(-3) (GSD = 3.4). The grain dust exposure levels were similar across workplaces and seasons, but the microbial content of the grain dust varied substantially between workplaces. Exposure levels of all microbial components were significantly higher in grain elevators compared with all other workplaces. The grain dust exposure was significantly correlated (Pearson's r) with endotoxin (rp = 0.65), β-1→3-glucan (rp = 0.72), bacteria (rp = 0.44) and fungal spore (rp = 0.48) exposure, whereas the explained variances were strongly dependent on the workplace. Bacteria, grain dust, and workplace were important determinants for endotoxin exposure, whereas fungal spores, grain dust, and workplace were important determinants for β-1→3-glucan exposure.
  
  
  CONCLUSIONS
  Although the workers were exposed to a relatively low mean dust level, the microbial exposure was high. Furthermore, the exposure levels of microbial components varied between workplaces although the dust levels were similar. We therefore recommend that exposure levels at different workplaces should be assessed separately and a task-based assessment should be done for detailed evaluation of efficient dust-reducing measures. The microbial content and knowledge of health effects of the microbial components should be considered in health risk evaluations of these workplaces.
authors.affiliation: Department of Chemical and Biological Work Environment, National Institute of Occupational Health, PO Box 8149 Dep, Oslo N-0033, Norway;
authors.forename: Anne Straumfors
authors.initials: AS
authors.lastname: Halstensen
authors.forename: Kari Kulvik
authors.initials: KK
authors.lastname: Heldal
authors.forename: Inge M
authors.initials: IM
authors.lastname: Wouters
authors.forename: Marit
authors.initials: M
authors.lastname: Skogstad
authors.forename: Dag G
authors.initials: DG
authors.lastname: Ellingsen
authors.forename: Wijnand
authors.initials: W
authors.lastname: Eduard
mesh_terms: D000328:Adult; D000391:Air Microbiology; D000395:Air Pollutants, Occupational / Q000032:analysis*; D004391:Dust / Q000032:analysis*; D002523:Edible Grain; D004731:Endotoxins / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D019649:Food Industry; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis; D009664:Norway; D016273:Occupational Exposure / Q000032:analysis*; D012044:Regression Analysis; D012621:Seasons; D047071:beta-Glucans / Q000032:analysis
chemical_list: D000395:Air Pollutants, Occupational; D004391:Dust; D004731:Endotoxins; D047071:beta-Glucans
keywords: endotoxin; fungal spores; grain industry; β-1→3-glucans